The present disclosure relates generally to data storage systems, and more particularly, but not by limitation, to data reassignment in data storage systems.
Data storage systems are used in a variety of different applications. Many different types of data storage systems exist, such as solid-state and non-solid state systems. Flash memory, random access memory (RAM), and dynamic random access memory (DRAM) are examples of solid-state data storage systems. Further, a disc drive is an example of a type of non-solid state storage system. A disc drive includes at least one rotating disc or storage medium for storage of digital information in a plurality of circular, concentric data tracks. Further, the data tracks (or similarly groups of locations in a solid state device) can be divided into a plurality of data sectors. The storage medium passes under a respective bearing slider surface. Each slider carries one or more transducers, which writes information to and reads information from the data surfaces of the disc(s). The slider and transducers are often together referred to as a “head.”
In some instances, one or more sectors of the storage medium can become defective. For example, it sometimes happens that sectors of a storage medium become defective during the manufacturing process of the storage medium. Further, in some instances sectors can become defective during normal operation. Defects can arise in any of the data sectors at various times during the lifetime of the storage system (grown defects). For a disc drive, grown defects include, for example, invading foreign particles which become embedded onto a surface of the storage medium, or external shocks to the storage system which can cause the transducer to nick or crash onto a surface of the storage medium. Defective data sectors pose either temporary or permanent data retrieval problems. To accommodate media defects such as grown defects, a number of spare sectors can be provided on the storage medium. The spare sectors are used to replace defective sectors on the storage medium.
In many embodiments, a data storage system is subjected to momentary shock and/or vibration which can cause data errors, for example during a data write and/or read operation. For example, data storage systems, such as disc drives, are recently being used to a greater extent in hand-held consumer electronics, such as digital music players, cell phones and personal data assistants. A disc drive in a hand-held device can undergo frequent shock events, such as accidental drops. In addition, some hand-held devices themselves are active shock generators. For example, a hand-held phone set on a vibration mode causes momentary shock events during vibration. Even a ring tone on a hand-held phone can provide a source of momentary shock if the volume is set high enough.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.